Neogoniolithon brassica-florida (encrusting rhodobionta) is generally reported as a veneering coral community along the wave-beaten rocky coast of the Mediterranean Sea. Its presence in the hyperhaline lagoon of Bahiret el Bibane, situated in SE Tunisia, takes on particular importance because of its extension. It constitutes a reef formation 14 km long developing on both sides of the sea inlet. The building of this “natural monument” seems to be the result of an evolutionary series. The aim of this study was to investigate the current status of this reef, comparing it to 30 years ago. The current extension of the Neogoniolithon brassica-florida reef appears to be much reduced from that reported 30 years ago, indicating a regression of 26%. Four different phases leading to the reef building were also identified.